UnusedExpressionResult: Report unused stdlib calls

[Shvandre]

Current behavior
No warning

Expected behavior

@name(__tact_store_bool)
extends native storeBit(self: Builder, value: Bool): Builder;

asm(cell self) extends fun storeRef(self: Builder, cell: Cell): Builder { STREF }

those functions are not marked with "mutates" keyword, so return value should be used.

Input source

contract Sample {
    receive("Test") {
        let x: Builder = beginCell();
        x.storeBit(true);
        x.storeRef(beginCell().storeUint(3, 5).endCell());
    }
}

Error report file
$ yarn misti ./tact.config.json -m info
$ /home/b4cksl4sh/TON-Studio/tact-template/node_modules/.bin/misti ./tact.config.json -m info
No errors found
Done in 0.89s.

[jubnzv]

I prefer to lower asm functions to something more convenient to use to don't rewrite the implementation later (requires #74)